The physical position of a device is an important piece of information. The physical position of the device may be useful for emergency services, as well as for improving the user experience. As an example, the ability to determine the physical position of the device may assist emergency services in locating the user of the device when the user is unable to respond to emergency responders. As another example, the physical position of the device may allow a service provider to provide suggestions for products, services, applications, advertisements, and so on, that may be useful to the user of the device.
Observed time difference of arrival (OTDOA) is a technique for determining the position of a device by measuring time differences between specific signals transmitted by other devices. OTDOA was introduced in the Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) series of technical standards. In OTDOA, positioning reference signals (PRSs) are transmitted by base stations, such as evolved NodeBs (eNBs) in 3GPP LTE, to allow user equipments (UEs) to measure time differences between PRSs transmitted by different base stations. However, in 3GPP LTE, the PRSs are transmitted by the eNBs periodically with periodicity and duration that are configured during the system planning and network management stages of the communications system. Therefore, the PRSs are transmitted even when UEs are not using the PRSs to determine their position, which is a waste of communications system resources.